Study of organic photovoltaics by localized concentrated sunlight (original) (raw)
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Applied Physics Letters, 2011
Structure dependence in hybrid Si nanowire/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) solar cells: Understanding photovoltaic conversion in nanowire radial junctions Appl. Phys. Lett. 100, 023112 (2012) Dependence of recombination mechanisms and strength on processing conditions in polymer solar cells APL: Org. Electron. Photonics 4, 279 (2011) Dependence of recombination mechanisms and strength on processing conditions in polymer solar cells Appl. Phys. Lett. 99, 263301 (2011) Crystal particle Raman-scattering and applications for improved solar cell performance Appl. Phys. Lett. 99, 251109 (2011) Effects of aging on the mobility and lifetime of carriers in organic bulk heterojunction solar cells J. Renewable Sustainable Energy 3, 063111 (2011) Additional information on Appl. Phys. Lett.
Japanese Journal of Applied Physics, 2012
We demonstrate high-efficiency hybrid solar cells based on heterojunctions formed between n-type silicon nanowires (SiNWs) and p-type organic semiconductors fabricated using a simple solution-based approach. Two types of devices have been fabricated with different organic materials used, namely poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and a small molecule, 2,2 0 ,7,7 0-tetrakis(N,N-di-4methoxyphenylamino)-9,9 0-spirobifluorene (Spiro-OMeTAD). The cells are characterized and compared in terms of their physical characteristics and photovoltaic performance. Using SiNWs of the same length of 0.35 m, it is found that the SiNWs/Spiro cells exhibit a power conversion efficiency of 10.3%, which is higher than the 7.7% of SiNWs/PEDOT cells. The results are interpreted in terms of the ability of the two organic semiconductors to fill the gaps between the SiNWs and the optical reflectance of the samples. The degradation of the SiNWs/Spiro cells is also studied and presented.
Nanoscale, 2014
Inorganic/organic hybrid radial heterojunction solar cells that combine vertically-aligned n-type silicon nanowires (SiNWs) with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) have great potential for replacing commercial Si solar cells. The chief advantage of such solar cells is that they exhibit higher absorbance for a given thickness than commercial Si solar cells, due to incident lighttrapping within the NW arrays, thus enabling lower-cost solar cell production. We report herein on the effects of NW length, annealing and surface electrode on the device performance of SiNW/PEDOT:PSS hybrid radial heterojunction solar cells. The power conversion efficiency (PCE) of the obtained SiNW/ PEDOT:PSS hybrid solar cells can be optimized by tuning the thickness of the surface electrode, and the etching conditions during NW formation and post-annealing. The PCE of 9.3% is obtained by forming efficient transport pathways for photogenerated charge carriers to electrodes. Our approach is a significant contribution to design of high-performance and low-cost inorganic/organic hybrid heterojunction solar cells.
Journal of Luminescence, 2015
We investigate the effects of Si nanowires surface modification with polystyrene (PS) on the performance of bulk heterojunction hybrid solar cells based on poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and PS-SiNWs. The optical, electrical and morphological properties of these hybrid nanocomposites have been investigated. Due to charge transfer efficiency, improved electrical coupling between SiNWs and MEH-PPV and homogeneous dispersion of functionalized SiNWs, the performance of studied photovoltaic structure shows a significant improvement with the progressive addition of PS-SiNWs. With polystyrene surrounded SiNWs as acceptor materials, the device typically shows a J SC of 7.36 mA/cm 2 , V OC of 0.87 V and a FF of 48% for the composition MEH-PPV:PS-SiNWs (1:4).
Si Nanowires Organic Semiconductor Hybrid Heterojunction Solar Cells Toward 10% Efficiency
ACS Applied Materials & Interfaces, 2012
High-efficiency hybrid solar cells are fabricated using a simple approach of spin coating a transparent hole transporting organic small molecule, 2,2′,7,7′-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD) on silicon nanowires (SiNWs) arrays prepared by electroless chemical etching. The characteristics of the hybrid cells are investigated as a function of SiNWs length from 0.15 to 5 μm. A maximum average power conversion efficiency of 9.92% has been achieved from 0.35 μm length SiNWs cells, despite a 12% shadowing loss and the absence of antireflective coating and back surface field enhancement. It is found that enhanced aggregations in longer SiNWs limit the cell performance due to increased series resistance and higher carrier recombination in the shorter wavelength region. The effects of the Si substrate doping concentrations on the performance of the cells are also investigated. Cells with higher substrate doping concentration exhibit a significant drop in the incident photons-to-current conversion efficiency (IPCE) in the near infrared region. Nevertheless, a promising short circuit current density of 19 mA/cm 2 and IPCE peak of 57% have been achieved for a 0.9 μm length SiNWs cell fabricated on a highly doped substrate with a minority-carrier diffusion length of only 15 μm. The results suggest that such hybrid cells can potentially be realized using Si thin films instead of bulk substrates. This is promising towards realizing low-cost and high-efficiency SiNWs/organic hybrid solar cells.
Bulk heterojunction organic-inorganic photovoltaic cells based on doped silicon nanowires
Journal of Experimental Nanoscience, 2008
Heterojunction photovoltaic devices were fabricated using single crystal silicon nanowires and the organic semiconductor regioregular poly-(3-hexyl thiophene) (RR-P3HT). N-type nanowires were first grown on an nþ silicon substrate by the vapor-liquid-solid (VLS) method. Devices were then fabricated by filling the gap between the nanowires and a transparent indium tin oxide (ITO) glass electrode with a polymer. For initial devices the gap was filled with P3HT deposited from chlorobenzene solution. Device performance indicates that both silicon and P3HT act as absorbers for photovoltaic response, but that photocurrents were very low due to high series resistance in the cell. A second type of device was fabricated by depositing a thin layer of P3HT on the grown nanowires by dip coating from a dilute solution, and then filling the voids between nanowires and the transparent electrode with the conductive polymer poly-[3,4-(ethylenedioxy)thiophene]: poly-(styrene sulfonate) (PEDOT:PSS). The relatively high mobility of this organic conductor results in much higher photocurrents in photovoltaic cells, but results in a dip in the spectral response of the cells in the blue-green region due to light absorption in the conducting polymer. These materials show promise for efficient low-cost photovoltaic devices, but the cell geometry and materials interfaces will need to be optimized to reach their potential.
Bulk Heteroj unction Organic-Inorganic Photovoltaic Cell Based on Doped Silicon Nanowires
CRC Press eBooks, 2019
Heterojunction photovoltaic devices were fabricated using single crystal silicon nanowires and the organic semiconductor regioregular poly-(3-hexyl thiophene) (RR-P3HT). N-type nanowires were first grown on an nþ silicon substrate by the vapor-liquid-solid (VLS) method. Devices were then fabricated by filling the gap between the nanowires and a transparent indium tin oxide (ITO) glass electrode with a polymer. For initial devices the gap was filled with P3HT deposited from chlorobenzene solution. Device performance indicates that both silicon and P3HT act as absorbers for photovoltaic response, but that photocurrents were very low due to high series resistance in the cell. A second type of device was fabricated by depositing a thin layer of P3HT on the grown nanowires by dip coating from a dilute solution, and then filling the voids between nanowires and the transparent electrode with the conductive polymer poly-[3,4-(ethylenedioxy)thiophene]: poly-(styrene sulfonate) (PEDOT:PSS). The relatively high mobility of this organic conductor results in much higher photocurrents in photovoltaic cells, but results in a dip in the spectral response of the cells in the blue-green region due to light absorption in the conducting polymer. These materials show promise for efficient low-cost photovoltaic devices, but the cell geometry and materials interfaces will need to be optimized to reach their potential.
2004
Polymer based solar cells were fabricated by using Poly(3-hexylthiophene-2.5diyl)(P3HT) as a donor, combined with the fullerene derivative [6,6]-phenyl-C 61 butyric acid methyl ester, (PCBM) as an acceptor, in a bulk heterojunction structure. Electrical and optical properties of these organic devices were studied together with the dependence of current-voltage characteristics on temperature and illumination intensity. The increase of the short circuit current density with temperature is evidence of a thermally activated transport mechanism, characteristic to disordered materials. This result explains the specific feature of organic solar cells to operate better in a warm climate, rather than at low temperatures, a totally different behaviour compared to conventional inorganic solar cells. The origin of open circuit voltage was investigated by varying the work function of the metallic electrode. From this experiment it was concluded that the open circuit voltage is very sensitive to the workfunction of metallic electrode. The hypothesis of Fermi level pinning of the workfunction of the metallic electrode to the LUMO level of the acceptor could not be confirmed in the case of P3HT:PCBM based solar cells. The thermal annealing applied to P3HT:PCBM based solar cells, was found to be a very effective method to increase the short current density, and therefore, the overall power conversion efficiency of the device. Morphology investigations (by using the Atomic Force Microscopy) for P3HT:PCBM based solar cells show the presence of large PCBM clusters (>500nm) built as a result of thermal annealing. Based on AFM results, as well as on current density-voltage (J-V) curves and external quantum efficiency measurements, the amount of the PCBM acceptor was optimized in the blend to a P3HT:PCBM weight ratio between 1:0.9 and 1:1. The best P3HT:PCBM based solar cell was fabricated with a P3HT:PCBM weight ratio of 1:1 and gave the following results: J sc = 6.4mA/cm², V oc = 0.59V, FF = 63.2%, η = 2.4% at room temperature and a white light intensity of 100mW/cm². Finally, it was shown that the electrical performance of P3HT:PCBM based solar cells can be considerably influenced by the quality of the organic material used for the fabrication. ZUSAMMENFASSUNG Es wurden Polymer-Solarzellen mit einer Bulk-Heteroverbindungsstruktur hergestellt, wobei P3HT als Donor und das Fullerenderivat PCBM als Akzeptor fungiert. Die elektrischen und optischen Eigenschaften dieser organischen Zellen wurden hauptsächlich über die Abhängigkeit ihrer Strom-Spannungs-Charakteristiken von Temperatur und Lichtintensität studiert. Die Zunahme der Kurzschlußstromdichte mit der Temperatur ist Beweis für einen thermisch aktivierten Transportmechanismus, der für ungeordnete Materialien charakteristisch ist. Dieses Ergebnis erklärt die hervorstechende Eigenschaft organischer Solarzellen in einem warmen Klima besser zu funktionieren, als bei tiefen Temperaturen. Konventionelle anorganische Solarzellen zeigen im Gegensatz dazu ein ganz anderes abweichendes Verhalten. Der Ursprung der Leerlaufspannung wurde durch Variation der Austrittsarbeit der Metallelektrode untersucht. Aus diesem Experiment konnte geschlossen werden, daß die Leerlaufspannung empfindlich von der Austrittsarbeit der verwendeten Metallelektrode abhängt. Die Hypothese des Fermi-Level-Pinnings der Austrittsarbeit der Metallelektrode an das Lumoniveau des Akzeptors hat sich im Falle der P3HT:PCBM Solarzellen nicht bestätigt. Die thermische Behandlung der P3HT:PCBM Solarzellen erwies sich als eine sehr effektive Methode zur Erhöhung der Kurzschlußstromdichte und damit auch als sehr wirkungsvoll zur Verbesserung des Gesamtwirkungsgrades der Zelle. Untersuchungen der Morphologie der P3HT : PCBM Solarzellen mittels AFM zeigen die Präsenz sehr großer PCBM Cluster (> 500 nm) als ein Resultat der thermischen Behandlung. Basierend auf diesen Ergebnissen, den J-V-Kurven und Messungen der externen Quantenausbeute wurde der Anteil des PCBM Akzeptors in der P3HT : PCBM-Mischung auf ein Gewichtsverhältnis zwischen 1:0,9 und 1:1 optimiert. Die beste P3HT:PCBM Solarzelle die hergestellt wurde, hatte ein Gewichtsverhältnis P3HT : PCBM von 1:1 und erzielte bei Raumtemperatur und einer Lichtintensität von 100 mW/cm² die folgenden Ergebnisse: J sc = 6.4mA/cm², V oc = 0.59V, FF = 63.2%, η=2.4% bei Raumtemperatur und einer Lichtintensität von 100mW/cm². Zusätzlich konnte gezeigt werden, daß die elektrischen Eigenschaften von P3HT : PCBM Solarzellen wesentlich durch die Qualität des verwendeten organischen Materials beeinflußt werden.